He said the party should be prepared to offer voters the chance of staying in the European Union if the Government fails to secure its promised trade deal with the remaining member states.

While the nation had backed Brexit in last year's referendum, he said he believed it was "possible" the public mood would change if it did not result in the promised benefits, and Labour should be ready to capitalise on that.

But Iain Duncan Smith said: “He is like a modern day Cassandra spreading doom and gloom when no one is listening to him.”

He added: “These voices from the past who led us into more and more difficulty I think it’s rather rich of them all to lecture modern day politicians on something that’s happened directly as a result of their own failure.”